As an achievement hunter I find it extremely disheartening that I cannot get the achievements without getting rid of all my progress in the game (100+ hours) and starting over. There are two achievements for sure I will never be able to do and two others I'm pretty sure are out of my reach now.
My suggestion (at least for Steam! I don't know if mobile users have the same game achievements but if so them too) is that an option to have an alternate/secondary save is added. This way players don't have to abandon all their hard work and/or investment (money/time/etc) in order to get achievements.
The secondary save could be something unlocked at a later chapter or be different in some way but still allow you to do the storyline in order to unlock missed achievements.